Glycerin and cashew and castor oils inclusion in the diets of Purunã bulls finished in feedlot on fatty acid percentage in the Longissimus dorsi

This work was carried out to study the glycerin and cashew and castor oils inclusion as natural additives on fatty acid composition of perirenal fat, subcutaneous fat and muscle Longissimus thoracis of Purunã bulls finished in feedlot for 252 days. A total of 32 Purunã bulls (11-12 ± 2.0 months; 202.8 ± 14.4 kg) were finished in feedlot with 4 diets (n = 8): CONT – basal diet; VOIL – basal diet and inclusion of vegetable oils (3 g/animal/day); GLYC – basal diet and inclusion of glycerin (20.1% glycerin in DM basis); GLVO – basal diet and inclusion of glycerin (20.1% glycerin in DM basis) and vegetal oils (3 g/animal/day). Glycerin inclusion reduced SFA, MUFA and PUFA levels in the diets. Glycerin and 1 In memoriam Ph.D. Department of Animal Science, State University of Maringá, Paraná, Brazil 2 PhD. Department of Chemistry Graduate Program, Federal Technological University of Paraná, Brazil 3 Ph.D. Department of Animal Science, State University of Maringá, Paraná, Brazil 4 Food Science Post-Graduate Program, State University of Maringá, Maringá, Brazil 5 Ph.D. Research – Department of Animal Science – Agronomic Institute of Paraná, Brazil 6 Ph.D. Professor – Department of Animal Science – State University of Maringá – 1A – CNPq fellowship, Maringá, Paraná, Brazil Research, Society and Development, v. 10, n. 13, e66101319844, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i13.19844 2 vegetable oils inclusion in the diets of bulls finished in feedlot did not change (P > 0.05) lauric, myristic, palmitic, docosanoic, n-7-tetradecenoic, palmitoleic, n-11 trans-vaccenic, oleic, n-7 cis-vaccenic, cis-9, t11 – CLA, n-3 docosapentaenoic and n-3 docosahexaenoic fatty acids levels in perirenal fat, subcutaneous fat and Longissimus thoracis muscle of bulls finished in feedlot. However, glycerin inclusion in the diets increased (P < 0.05) pentadecanoic, margaric and n-9, cis-10 heptadecanoic fatty acids levels when compared of perirenal fat, subcutaneous fat and Longissimus thoracis muscle of bulls fed CONT and VOIL diets. On the other hand, glycerin inclusion decreased (P < 0.05) linoleic fatty acid in perirenal fat, subcutaneous fat and Longissimus thoracis muscle in comparison of CONT and VOIL diets. Glycerin and vegetables oils inclusion in the diets did not alter (P > 0.05) SFA and MUFA levels in perirenal fat from bulls fed four diets. The PUFA, n-6 and n-3 levels and PUFA:SFA and n-6:n-3 ratios were similar (P > 0.05) between perirenal fat of bulls fed CONT and VOIL diets and greater (P < 0.05) when compared of perirenal fat from bulls fed GLYC and GLVO diets. SFA, MUFA levels and n-6 and n-3 ratios were similar (P > 0.05) among all diets. PUFA and MUFA levels in fat subcutaneous and n-6:n3 ratio were similar (P > 0.05) between GLYC and GLVO diets, but greater than CONT and GLYC diets. Total fatty acids sum levels in Longissimus thoracis muscle were similar (P > 0.05) among bulls from all diets, except the lowest levels in bulls from GLYC and GLVO diets in comparison to CONT and VOIL diets. In conclusion glycerin inclusion in the diets modifies fatty acids in fat and muscle of bulls finished in feed-lot.


Introduction
Fat is important nutrient in the diet, improves palatability food, increases vitamins and carotenoids absorption. However, high intakes of saturated fats are a risk factor for several chronic diseases, such as cardiovascular disease, obesity, diabetes and cancer. According HMSO (1994) to adequate food, the daily intake of fat should not exceed 35% of the total diet from different food sources. In Brazil, red meat has an important nutritional value in human diet (Eiras et al., 2017;Guerrero et al., 2018;Vital et al., 2018). In recent year's research on livestock production are concerned to improve meat quality (Cruz et al., 2014;Eiras et al., 2014b;Monteschio et al., 2017;Valero et al., 2014). However, its demand high investments, technology and alternatives feed .
Crude glycerin is an excellent energy source by corn partial replacing in the diets for beef cattle (Cruz et al., 2014;Eiras et al., 2014a;Eiras et al., 2014b;Françozo et al., 2013). In metabolism animal, glycerol increases in the gluconeogenesis which improve synthesis of glucose in the liver. Furthermore, provide energy for cellular metabolism and increase fat deposition. Red meat has high fatty acids saturated contents Rotta et al., 2009). In general, fatty acids polyunsaturated food contents is extensively metabolized by microorganisms and bio-hydrogenated which resulting in stearic acid production (Wu & Palmquist, 1991) and deposition on and into muscle.
Other products are widely researched around the world in order to improve ruminal parameters and decrease fatty acids saturated production. According Cruz et al. (2014) and Valero et al. (2016) the association of the compounds extracted from cashew and castor oils, the similar effects were observed in comparison the sodium monensin. Essential oils contain secondary metabolites (terpenoids and phenolic compounds) that confer antimicrobial action on gram-positive and gram-negative bacteria (Benchaar et al., 2008). Cashew and castor oil contain high percentage of compounds whit characteristics that confer antimicrobial action. Previous studies reported antimicrobial action is attributed by interacting of compounds with the bacteria cell membrane, such ion gradients, electron transport, protein translocation, phosphorylation and enzyme-dependent reactions (Benchaar et al., 2008;Ultee et al., 2000). Castor oil contain high percentage of ricinoleic acid, which confer antimicrobial properties; whereas, cashew contain high percentage of anacardic acid and lower proportion cardol and cardanol acids. These compounds in cashew confers antibacterial, antioxidant and anti-parasitic (Kubo et al., 1999) activities. Previous studies reported by Ultee et al. (2000) show that synergisms between compounds extracted from different products increase antibacterial activity.
Thus, the synergism between compounds in cashew and castor oils may improve the antimicrobial effect on microorganisms.
However, the results are unclear on fatty acids contents in the meat.
This study was realized to evaluate corn grain replacing by glycerin with 812 g of glycerol per kg/DM contained, and vegetal oils from cashew and castor oils extract produced in northern Brazil on fatty acids composition in fat perirenal, fat subcutaneous and in Longissimus thoracis muscle of Purunã young bulls finished in feedlot for 252 days. Research, Society andDevelopment, v. 10, n. 13, e66101319844, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i13.19844

Ethic committee, Local, animals, diets and experimental design
The present experiment was approved by the Department of Animal Science of the State University of Maringá and performed at the Experimental Farm of the Agronomic Institute of Paraná, Ponta Grossa city, Paraná state, Brazil south, and followed the guidelines of biomedical research with animals (CIOMS/OMS, 1985) (Protocol -550.891-2010-2/CNPq).
Experimental design was composited of four treatments: CONTdiet without glycerin; VOILdiet with cashew and castor oils (3 g/animal/day); GLYCdiet with glycerin (20.1% glycerin in DM basis), and GLVOdiet with glycerin (20.1% glycerin in DM basis and vegetal oils -3 g/animal/day). Each experimental treatment comprised 8 Purunã young bulls. It was performed an adaption period for 21 days and during time which the bulls were fed corn silage and concentrate (40:60 ratio, respectively). Concentrate base containing soybean meal, corn grain and mineral salt ad libitum. The bulls were given access to a diet formulated provide a weight gain of 1.0 kg/day and meet requirements for fattening beef cattle.
The feeds were offered half in the morning at 0800 h and half in the afternoon at 1500 h. The concentrate intake was fixed in BW 1.4% adjusted at the 28-d. Samples of offered corn silage, concentrate was collected twice weekly for estimations of DM%.
The glycerin was produced in a soy-diesel facility and the chemical composition was determined in an Institute of Technology of Paraná. Glycerin contained (g/kg, as-fed) 23.2 water, 4.76 ashes, 812 glycerol, 11.63 Na and (mg/kg, as-fed) 3.3 methanol, 79.1 k, 35.8 Cl,16.3 Mg,239 P,and 3.65 Mcal/kg of crude energy. Glycerin feed in the current study was used as an energetic ingredient; therefore, to obtain four isoenergetic diets, the glycerin level was counterbalanced, mainly by a decrease in corn grain content (Table 1). The vegetal oils contain ricinoleic acid, anacardic acid, cardanol and cardol. Ricinoleic acid was obtained from castor oil (extracted from castor seed) and anacardic acid, cardanol and cardol from the cashew both were produced in northern Brazil. Vermiculite was used for solidification of vegetal oils. The mix of vegetal oils was realized in Laboratory of analysis Oligo Basics Agroindustrial Ltda. It was used 3 g/animal/day. All diets were formulated to be isonitrogenous (Table 2).

Performance and carcass characteristics
The animals were weighed at the beginning of the experiment and then every twenty-eight days after a fasting from solid food period of 16 hours, until the end of the experiment (252 days), in order to determine animal performance and carcass characteristics.

Sampling
The bulls were slaughtered at a commercial slaughterhouse 10 km from Ponta Grossa Research Farm, with the same age (20 + 2 months) according to industrial practices in Brazil, when the bulls reached a final BW of 468.4 + 31.5 kg.
At slaughter perirenal fat samples was separated and frozen at -20 o C for later analysis. After chilling (24h at 4 o C), the right part of the carcass was used to determine the quantitative and qualitative characteristics of LT. Perirenal fat, fat subcutaneous and LT samples were taken by complete cross-section between the 12 th and 13 th ribs and were immediately taken to the laboratory. From LT samples, fat subcutaneous was separated and the muscle and fat portions were frozen at -20 o C for later analysis.

Extraction and preparation of fatty acid methyl ester
Total lipids were extracted with a chloroform/methanol (2:2:1.8 v/v/v) mixture. Fatty acid methyl esters (FAME) were prepared by triacylglycerol methylation. After that, the esters were extracted with 2 mL of n-heptane and freeze stored at -18° C for later chromatographic analysis.

Chromatographic analysis
Methyl ester was separated by gas chromatography using a Thermo 3300 gas chromatograph fitted with a flame ionization detector (FID) and a CP-7420 fused-silica capillary column (100 m x 0.25 mm i.d. x 0.25 µm of cyanopropyl, SELECT FAME). The operation parameters were as follows: detector temperature 240 o C, injection port temperature 230 o C, column temperature 165 o C for 18 min, programmed to increase at 4 o C min -1 up to 235 o C, with final holding time of 14.5 min, carrier gas, hydrogen at 1.2 mL min -1 , nitrogen makeup gas at 30 mL min -1 , split injection at 1:80 ratio. For identification, the retention times of the fatty acids were compared to those of standard methyl esters (Sigma, St. Louis, MO). Retention times and peak area percentages were automatically computed with Software Chronquest 5.0. The fatty acid composition on perirenal fat, Longissimus thoracis muscle and fat thickness were expressed as percentage.

Enzyme activities ∆9 desaturase
The ∆9 , 1997). The index EA uses all of the nonessential C18 fatty acids as a proportion of both C16 and C18 fatty acids expressed as percentage.

Statistical analysis
The experimental design was completely randomized, with four diets and eight replicates. All variables were submitted to a normality test using the Univariate procedure of SAS (Version 9.1.2, SAS Institute; Cary, NC, USA). The variables were tested for conformity to normal distributions using the Shapiro-Wilk test at W > 0.90. Data were analyzed using the MIXED procedure of SAS (Version 9.1.2, SAS Institute). The model statement contained the fixed effect of diet. Data were analyzed using bull as the random variable. Results are reported as least-squares means and were separated using PDIFF. Significance was set at P < 0.05.
The glycerin inclusion (GLYC and GLVO diets) increased (P < 0.02; +39%) the pentadecanoic (15:0) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the pentadecanoic fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The glycerin inclusion in the diets (GLYC and GLVO diets) increased (P < 0.01; +35%) the margaric (17:0) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the margaric fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The glycerin inclusion in the diets (GLYC and GLVO diets) decreased (P < 0.05; -11%) the stearic (18:0) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the stearic fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The tetradecenoic (14:1 n-7) fatty acid percentage was lower (P < 0.01; -77%) in the perirenal fat of bulls finished with VOIL diet in comparison of bulls finished with others three diets (Table 4). However, the tetradecenoic fatty acid percentage was similar (P > 0.05) in the perirenal fat of bulls finished with CONT, GLY and GLVO diets.
The glycerin inclusion in the diets (GLYC and GLVO diets) decreased (P < 0.03; -23%) the pentadecanoic (15:1 n-9) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the pentadecanoic fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The glycerin inclusion in the diets (GLYC and GLVO diets) increased (P < 0.02; +57%) the heptadecanoic (17:1 n-9, cis-10) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the pentadecanoic fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The glycerin inclusion in the diets (GLYC and GLVO diets) decreased (P < 0.03; -60%) the linoleic -LA (17:2 n-6) fatty acid percentage in the perirenal fat in comparison to bulls fed CONT and VOIL diets (Table 4). Still, the linoleic fatty acid percentages were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
However, the PUFA:SFA and n-6:n-3 ratios were similar (P > 0.05) between perirenal fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The PUFA:MUFA ratio in the fat subcutaneous did not change (P > 0.06) among diets (Table 5). However, the n-6:n-3 ratio was lower (P < 0.04; -19%) in the fat subcutaneous of bulls fed glycerin inclusion in the diets in compassion of fat subcutaneous of bulls with CONT and VOIL diets. Still, the n-6:n-3 ratio were similar (P > 0.05) between subcutaneous fat of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.
The Δ 9 -desaturase (C16) and elongase enzyme activities were similar (P > 0.05) in the LT muscle of bulls finished with four diets (Table 6). However, the Δ 9 -desaturase (C18) enzyme activity in the LT muscle was higher (P < 0.03) in the LT muscle of bulls finished of glycerin inclusion (GLYC and GLVO diets) in comparison of CONT and VOIL diets (Table 6). Still, the Δ 9desaturase (C18) value was similar (P > 0.05) between LT muscle of bulls finished with CONT and VOIL diets and GLYC and GLVO diets.

Discussion
The experimental design allowed a young bull's production and examination of corn grain replaced by glycerin as energy source and vegetal oils as natural compounds on fatty acids composition in the perineal and subcutaneous fat and Longissimus thoracis (LT) muscle. At the beginning of the experiment, it was observed changes in fatty acid percentage in the diets when replaced corn grain by glycerin (Table 3). Diets with glycerin decrease SFA (13.2%), MUFA (26.1%) and PUFA (20.2%).
The bulls were slaughter 20 month's age and a finishing period 252 days in feedlot. In contrast, feedlot practices in Brazil usually range 24 to 28 months and period about 4 months (Françozo et al., 2013;Zawadzki et al., 2011). Previous studies reported meat fatty acid composition is influenced by genetic groups ) and dietary factors (Padre et al., 2006(Padre et al., , 2007Smet et al., 2004). According, De Smet et al. (2004) the percentages of SFA and MUFA content increases faster with increasing fatness than does the content of PUFA. Thus, it was selected animals of same genetic group (¼ Aberdeen Angus + ¼ Caracu + ¼ Charolais + ¼ Canchim) to reduce the effect hereditary on fat deposition.
Manipulation of fatty acids composition through feeding is usually more practical and cost effective compared to new breeding strategies. Fat deposition occurs at different stages of growth, which is observed greats rate of deposition in internal fat followed intramuscular, subcutaneous and intramuscular. Previous study (Eiras et al., 2014b;Françozo et al., 2013;Prado et al., 2016;Silva et al., 2017) report increased intramuscular fat and fat thickness, whereas any effect on total lipids in the LT in response to glycerin and vegetal oils inclusion in the diets.
The free glycerol in the blood stream is metabolized in the liver to glycerol-3-phosphate by glycerol kinase enzyme, which is used to triacylglycerol and phospholipids synthesis. According De Smet et al. (2004) the phospholipids content is independent of the total fat content while triacylglycerol is strongly correlated with the total fat content. Likewise, Aldai et al. (2007) reported that intramuscular fat constituted the most homogenous adipose tissue in response different genotypes. In general, ruminant meat contains higher percentage of 16:0 and 18:0 fatty acids (Aricetti et al., 2008;Ducatti et al., 2009;Prado et al., 2003).

Perirenal fat
In the total sum of saturated fatty acids (SFA) there was no effect of glycerin and vegetable oils inclusion in the diets in the perirenal fatty acid percentage, although the total sum of saturated fatty acids was high (63%). Similarly, the glycerin and vegetable oils inclusion in the diets of bulls finished in feedlot had little influence on individual saturated fatty acids percentage in the perirenal fat, except for the increase of margaric fatty acid and reduction of stearic fatty acid. The reduction of stearic acid in the perirenal fat probably occurs due lower proportion of total fatty acid in diets with glycerin (Table3).
As observed to saturated fatty acids, in the total sum of monounsaturated fatty acids there was no effect of glycerin and vegetable oils inclusion in the diets in the perirenal fatty acid percentage. However, the MUFA was low (34%) when compared with MUFA percentage in the subcutaneous fat and Longissimus muscle from the same animals. However, the glycerin and vegetable oils inclusion in the diets increased cis-10-heptadecaenoic fatty acid and decreased pentadecanoic fatty acid in the perirenal fat. Thus, the glycerin and vegetable oils inclusion in the diets had small meaning on MUFA in the perirenal fat of bulls. The lower percentage of MUFA in the perirenal fat probably is due higher metabolizing of glycerol to triacylglycerol.
However, in currently study no was determined phospholipids and triacylglycerol content in the perirenal fat. The triacylglycerol contains much lower amounts of MUFA, whereas are rich in PUFA (Smet et al., 2004) due phospholipids as constituents of the cell membrane.
On the other hand, the glycerin and vegetable oils inclusion in the diets (GLYC and GLVO diets) decreased polyunsaturated fatty acid (PUFA) percentage in the perirenal adipose tissue of bulls in comparison to CONT and VOIL diets due to the lower percentage of the individual polyunsaturated fatty acids linoleic and α-linolenic.
The PUFA:MUFA and n-6:n-3 ratios in the perirenal adipose tissue of bulls were lower with glycerin and vegetable oils inclusion in the diets in comparison to CONT and VOIL diets due to the lower percentage of the PUFA and n-6 fatty acids. The reduction of PUFA, total n-6 and n-3, PUFA:SFA and n-6:n-3 ratios can be explained by fatty acids content in diets (Table 3).
The glycerin and vegetable oils inclusion in the diets decreased n-6 and n-3 fatty acids percentage in the perirenal adipose tissue of bulls in comparison to CONT and VOIL diets.
On the other hand, we observed higher Δ 9 -desaturase enzyme (C18) activity in diets with glycerin and lower activity in CONT and VOIL diets. The Δ 9 -desaturase convert stearic fatty acid into the n-9 monounsaturated fatty acid oleic (Malau-Aduli et al., 1997).
However, we observed increase of elongase enzyme activity in VOIL diet and decreased in GLVO diet (Table 4). The levels of stearic acid on perirenal fat can be explained by elongase enzyme activity (Table 4).

Fatty acid in the subcutaneous fat
The diversity of fatty acids in the subcutaneous fat is partly explained by biohydrogenation reactions in the rumen (Benchaar et al., 2001;Tamminga & Doreau, 1991). In the total sum of saturated fatty acids there was no effect of glycerin and vegetable oils inclusion in the diets on fatty acid percentage in the subcutaneous fat. Similarly, the glycerin and vegetable oils inclusion in the diets of bulls finished in feedlot had little influence on individual saturated fatty acids percentage in the subcutaneous fat, except for the increase of pentadecanoic and margaric fatty acid. According Zock et al. (1994) lauric, myristic and palmitic fatty acid increase serum total cholesterol and low-density lipoprotein levels, whereas stearic, oleic and linoleic fatty acids decrease serum total cholesterol and low-density lipoprotein levels. Carvalho et al. (2014) did not observe changing in saturated fatty acids when the glycerin was included up to 18% in the diets of young bulls finished in feedlot.
As observed to saturated fatty acids, in the total sum of monounsaturated fatty acids there was no effect of glycerin and Previous study reported elongase enzyme activity on 16:0 to 18:0 (Malau-Aduli et al., 1997). However, any difference was observed on 16:0 and elongase activity both tissues (Table 6 and 7). On the other hand, diets with glycerin (GLY and GOL) increase 18:1 n-9 on LT (Table 6). These results on LT can be explained by results obtained in Δ 9 -desaturase (18) enzyme activity (Table 6), which is important enzyme in the synthesis of monounsaturated fatty acids in bovine tissue (Chang et al., 1992). In contrast, Eiras et al. (2014b) reported any difference on C18:1 n-9 acid in the LT in response glycerin levels.
The glycerin and vegetable oils inclusion in the diets decreased n-6 and did not effect on n-3 fatty acid percentage in the subcutaneous fat of bulls in comparison to CONT and VOIL diets.
The PUFA:MUFA ratio in the fat subcutaneous of bulls were similar and n-6:n-3 ratio was lower with glycerin and vegetable oils inclusion in the diets in comparison to CONT and VOIL diets due to the lower percentage of the PUFA and n-6 fatty acids. The reduction of PUFA, total n-6 and n-3, PUFA:SFA and n-6:n-3 ratios can be explained by fatty acids content in diets (Table 3).

Fatty acid in the Longissimus thoracis (Lt) muscle
Total sum saturated fatty acids (SFA) in the LT muscle were showed in Table 6. The percentage of SFA was similar in the LT muscle among four diets. Thus, the glycerin and vegetable oils addition in the diets did not alter the SFA in LT muscle as observed by Françozo et al. (2013), Prado et al. (2016) and Silva et al. (2017) in the LT muscle from animals finished to up 18% of glycerin in the diets. However, other authors (Carvalho et al., 2014; observed a reduction of SFA in the LM muscle of bulls finished in feedlot and fed with glycerin addition in the diets. On the other hand, the glycerin + vegetable oils in the diets increased the pentadecanoic and margaric fatty acids and decreased the stearic fatty acid. As observed to SFA, the glycerin and vegetable oils in the diets did not alter the monounsaturated fatty acids (MUFA) in the LT muscle of bulls. Thus, the glycerin addition in the diets did not alter the SFA as observed by Françozo et al. (2013), Prado et al. (2016) and Silva et al. (2017) in the LT muscle from animals finished to up 18% of glycerin in the diets. However, other authors (Carvalho et al., 2014; observed a reduction of SFA in the LM muscle of bulls finished in feedlot and fed with glycerin addition in the diets. On the other hand, the glycerin + vegetable oils in the diets increased the heptadecanoic and oleic fatty acids and decreased the trans-vaccenic fatty acid. In general, these fatty acids have low concentration in LT (Padre et al., 2006(Padre et al., , 2007. Previous study reported 18:1 n-9 most prominent MUFA occurring mainly as cis and trans isomers. The levels of trans-vaccenic fatty acid increase when vegetable oil was added in glycerin diet in the LT. Previous studies reported trans-vaccenic fatty acid as an important intermediate produced by microorganisms in the biohydrogenation of fatty acids in the rumen, which is precursor of CLA (Griinari & Bauman, 1999). Likewise, other study showed beneficial health effects of CLA in humans.
The observed increase in fatty acids such as pentadecanoic (C15:0), margaric (C17:0), and heptadecanoic (C17:1) acids is of interest for human health, because these lipids of microbial origin inhibit the growth of cancer cells. Glycerin increases ruminal propionate content and may promote the production of odd-chain fatty acids. Other authors found an increase in margaric acid concentration in meat from grazing cattle when animals received supplementary crude glycerin (San Vito et al., 2015).
This increase may be due to a higher amount of margaric acid with increase glycerin concentration in the diet (Table   3). A similar result was found by Lage et al. (2014), who reported an increase in the concentration of margaric acid when 10% glycerol was included in the diet of Nellore cattle finished in feedlots. Margaric acid does not have a high impact on serum cholesterol levels, as lauric (C12:0) and myristic (C14:0) saturated fatty acids; thus, increasing the margaric acid in meat does not cause risks to human health.
The total sum of polyunsaturated fatty acids (PUFA) was similar when the glycerin and vegetable oils were included in the diets. However, the glycerin and vegetable oils inclusion in the diets reduced linoleic, arachidonic and eicosapentaenoic fat acids in the LT muscle. Still, the glycerin and vegetable oils only did not affect the CLA, γ-linolenic, DPA and DHA fatty acids percentages, but the glycerin and vegetable oils addition together (GLVO diet) reduced the α-linolenic fatty acid percentage.
Diets in presents study contain high values of LA and LNA fatty acid (Table 3); however, these fatty acids are intensively bio hydrogenated by microorganisms to stearic fatty acid in the rumen (Griinari & Bauman, 1999). Previous studies with different compounds extract by plants reported modification on ruminal fermentation (Yang et al. 2010). On the other hand, previous studies reported LA and LNA as essential in human diet; which are elongated and desaturated to long-chain PUFA's, to DHA, AA and EPA (Spector, 1999). Results in currently study showed higher levels of AA in diets with glycerin and higher levels of EPA in CONT and VOIL diets on LT, whereas DHA any difference was observed. However, these values are below adequate diet. According HMSO the recommended daily intake of EPA and DHA for adults ranges between 200 to 680 mg/d in several countries. These fatty acids are important to maintain cell membrane structure and physiological function.
Likewise, we observed higher values for total n-6 in diets without glycerin and vegetable oils (CONT and VOIL diets).
However, the n-3 fatty acid was similar among four diets. Thus, the glycerin and vegetable oils addition decreased the n-6 fatty acid percentage and maintain the n-3 fatty acid percentage. Likewise, Aldai et al. (2007) reported similar values for n-6:n-3 ratio in LT muscle.
Results in currently study showed lower values of PUFA:SFA ratio (0.15) and higher levels of n-6:n-3 (3.33) ratio in LT muscle. However, PUFA:SFA ratio is below an adequate diet. On the other hand, n-6:n-3 ratio is adequate for consumption human. According HMSO (1994), the PUFA:SFA ratio should be above 0.45 and n-6:n-3 ratio lower than 4.0. Likewise results indicate that fatty acids essentials in human diet were observed for diets without glycerin (LA) and VOIL diet (LNA) on LT.
The diversity of fatty acids in the LT muscle is partly explained by biohydrogenation reactions in the rumen (Benchaar et al., 2001;Tamminga & Doreau, 1991).
Any difference was observed on Δ 9 -desaturase (16) and elongase activities in the LT muscle tissues. However, the Δ 9desaturase (18) was increased by diets with glycerin and vegetable inclusion (GLY and VOIL diets). These results on LT can be explained by results obtained in Δ 9 -desaturase (18) enzyme activity (Table 6), which is important enzyme in the synthesis of monounsaturated fatty acids in bovine tissue (Chang et al., 1992). In contrast, Eiras et al. (2014b) reported any difference on C18:1 n-9 acid in the LT in response glycerin levels.

Conclusion
Corn grain replacement by glycerin with 81.2% of glycerol might be fed to finishing bulls in feedlot change fatty acid composition on fat perirenal, Longissimus thoracis muscle and fat thickness. The glycerin inclusion reduces the levels of SFA, MUFA and PUFA in total diet. Diets did not change lauric, myristic and palmitic in Longissimus thoracis muscle and fat subcutaneous. On the other hand, diets with glycerin reduce levels of stearic acid on perirenal fat, Longissimus thoracis muscle and fat thickness. Likewise, levels of linoleic acid reduce with glycerin inclusion on perirenal fat, Longissimus thoracis muscle and fat thickness. Diets without glycerin or with FO improve linoleic, α-linolenic and eicosapentaenoic acids on Longissimus thoracis muscle and fat thickness. Total PUFA, n-6 and PUFA:SFA and n-6:n-3 ratio improves with FO addition on fat thickness.
Diets without glycerin and vegetable higher levels of SFA, PUFA and n-6 on Longissimus thoracis muscle. In general diets FO addition or no in diets without glycerin improve fatty acids on all tissues.